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Ch.12 - Parametric and Polar Curves
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Non è quello che usi tu?Cambia libro di testo
Capitolo 12, Problema 12.1.73

73–76. Tangent lines Find an equation of the line tangent to the curve at the point corresponding to the given value of t.


x=t ²−1, y=t ³ +t; t=2

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Identify the parametric equations given: \(x = t^{2} - 1\) and \(y = t^{3} + t\), and the value of the parameter \(t = 2\) at which we want the tangent line.
Find the derivatives of \(x\) and \(y\) with respect to \(t\): compute \(\frac{dx}{dt}\) and \(\frac{dy}{dt}\). For \(x = t^{2} - 1\), \(\frac{dx}{dt} = 2t\). For \(y = t^{3} + t\), \(\frac{dy}{dt} = 3t^{2} + 1\).
Calculate the slope of the tangent line \(\frac{dy}{dx}\) at \(t=2\) using the chain rule for parametric equations: \(\frac{dy}{dx} = \frac{\frac{dy}{dt}}{\frac{dx}{dt}}\) evaluated at \(t=2\).
Find the coordinates of the point on the curve at \(t=2\) by substituting \(t=2\) into the parametric equations: \(x(2)\) and \(y(2)\).
Use the point-slope form of the line equation with the point \((x(2), y(2))\) and slope \(\frac{dy}{dx}\) to write the equation of the tangent line: \(y - y(2) = m (x - x(2))\), where \(m\) is the slope found in the previous step.

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Parametric Equations

Parametric equations express the coordinates of points on a curve as functions of a parameter, often denoted as t. Here, x and y are given in terms of t, allowing us to analyze the curve's behavior by varying t.
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Parameterizing Equations

Derivative of Parametric Curves

To find the slope of the tangent line to a parametric curve, we compute dy/dx as (dy/dt) divided by (dx/dt). This ratio gives the instantaneous rate of change of y with respect to x at a specific parameter value.
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Differentiation of Parametric Curves

Equation of a Tangent Line

Once the slope of the tangent line and the point of tangency are known, the tangent line's equation can be written using the point-slope form: y - y₀ = m(x - x₀), where m is the slope and (x₀, y₀) is the point on the curve.
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Equations of Tangent Lines